Is it your first salt water tank? I recommend to wait a while until you can maintain stable parameters, which can be difficult in such a small tank. What kind of lighting do you have? Nems require high lighting and pristine water. It may also be tricky to house in your tank as they do grow quite large. I have 2 in my 55 and ate both bigger than my open hand what else is in there?

One in a 3 gallon sounds more like a trap. It'd be quite difficult to keep the water pristine like anemones need with such a small water column. Not even sure where you'd find a light that would work for such a small tank that would be intense enough.

That has a 9W CF 50/50 bulb that they say can support mushrooms and zoas. As those are the lowest light requiring corals, anemones are out of the question. But there are some Awwwwsome zoa designs out there. An assortment of differing zoa colours would look nice on a desk. And your water paramenters are not near as critical as for an anemone.